Voltage conversion device, voltage conversion method, and computer-readable recording medium containing program causing computer to execute voltage conversion

ABSTRACT

A control device receives an output voltage of a voltage-up converter from a voltage sensor, and calculates a feedback preliminary voltage control value determined by the difference between a voltage control value and the output voltage. The control device corrects the calculated feedback preliminary voltage control value in accordance with the output voltage to calculate a feedback voltage control value where the follow-up property of the output voltage with respect to the voltage control value is equal to a reference property. The control device controls the voltage-up converter using a feedback voltage control value. The voltage-up converter converts a direct current voltage from a DC power supply into the output voltage maintaining the follow-up property of the output voltage with respect to the voltage control value at the reference property.

TECHNICAL FIELD

The present invention relates to a voltage conversion apparatusconverting a direct current voltage from a DC power supply into adesignated voltage, a voltage conversion method of converting a directcurrent voltage into a designated voltage, and a computer-readablerecording medium with a program recorded thereon to allow a computer toexecute control of voltage conversion for converting a direct currentvoltage into a designated voltage.

BACKGROUND ART

Hybrid vehicles and electric vehicles are now attracting considerableattention as automobiles taking into account environmental matters. Somehybrid vehicles are now commercially available.

Such hybrid vehicles employ a DC power supply, an inverter, and a motordriven by the inverter as well as a conventional engine, as the powersource. Specifically, power is generated by driving the engine, as wellas by the rotation of the motor based on converted alternating voltage,achieved by conversion of a direct current voltage from a DC powersupply by means of an inverter. An electric vehicle employs a DC powersupply, an inverter, and a motor driven by the inverter as the powersource.

In such hybrid vehicles and electric vehicles, an approach is known toboost a direct current voltage from a DC power supply by a voltage-upconverter, and supplying the boosted direct current voltage to theinverter that drives the motor (for example, Japanese Patent Laying-OpenNo. 2001-275367).

Specifically, a hybrid vehicle or an electric vehicle incorporates amotor driver shown in FIG. 23. Referring to FIG. 23, a motor driver 300includes a DC power supply B, system relays SR1 and SR2, capacitors C1and C2, a bidirectional converter 310, a. voltage sensor 320, and aninverter 330.

DC power supply B outputs a direct current voltage. System relays SR1and SR2 supply the direct current voltage from DC power supply B tocapacitor C1 when turned on by a control device (not shown). CapacitorC1 smoothes the direct current voltage supplied from DC power supply Bvia system relays SR1 and SR2, and supplies the smoothed direct currentvoltage to bidirectional converter 310.

Bidirectional converter 310 includes a reactor 311, NPN transistors 312and 313, and diodes 314 and 315. Reactor 311 has one end connected to apower supply line of DC power supply B and its other end connected at anintermediate point between NPN transistors 312 and NPN transistors 313,i.e. between the emitter of NPN transistor 312 and the collector of NPNtransistor 313. NPN transistors 312 and 313 are connected in seriesbetween the power supply line and the ground line. The collector of NPNtransistor 312 is connected to the power supply line. The emitter of NPNtransistor 313 is connected to the ground line. Further, diodes 314 and315 conducting a current from the emitter side to the collector side areconnected between the collectors and emitters of NPN transistors 312 and313, respectively.

Bidirectional converter 310 has NPN transistors 312 and 313 turnedon/off by a control device (not shown) to boost the direct currentvoltage from capacitor C1 and provide the output voltage to capacitorC2. When the hybrid vehicle or electric vehicle in which motor driver300 is incorporated is under regenerative braking, bidirectionalconverters 310 is powered by alternating current motor M1 todown-convert the direct current voltage converted by inverter 330 andsupply the down-converted voltage to capacitor C1.

Capacitor C2 smoothes the direct current voltage from bidirectionalconverter 310 to provide the smoothed direct current voltage to inverter330. Voltage sensor 320 detects the voltage across capacitor C2, i.e.the output voltage Vm of bidirectional converter 310.

When direct current voltage is supplied from capacitor C2, inverter 330converts the direct current voltage into alternating voltage undercontrol of a control device (not shown) to drive alternating currentmotor M1. Accordingly, alternating current motor M1 is driven togenerate the torque specified by a torque control value. When the hybridvehicle or electric vehicle in which motor driver 300 is incorporated isunder regenerative braking, inverter 330 converts the alternatingvoltage generated from alternating current motor M1 into a directcurrent voltage under control of the control device to supply theconverted direct current voltage to bidirectional converter 310 viacapacitor C2.

When the direct current voltage output from DC power supply B is boostedand the output voltage Vm is to be provided to inverter 330 in motordriver 300, feedback control is effected so that output voltage Vmdetected by voltage sensor 320 is equal to a voltage control valueVdccom. This feedback control is PI control. The PI control gain isdetermined so that output voltage Vm is equal to voltage control valueVdccom.

In such a conventional motor driver, the PI control gain is determinedand feedback control is effected employing the determined PI controlgain to set the boosted output voltage Vm equal to voltage control valueVdccom.

When the PI control gain is determined under a certain condition andcontrol is fixed to the determined PI control gain, any change in outputvoltage Vm and voltage control value Vdccom will cause variation in theadjustment of the voltage applied across NPN transistor 313 inaccordance with output voltage Vm even if the difference between outputvoltage Vm and voltage control value Vdccom is constant. As a result,the problem of variation in the follow-up property of output voltage Vmwith respect to voltage control value Vdccom will occur.

DISCLOSURE OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide a voltage conversion apparatus converting a direct currentvoltage into an output voltage such that the follow-up property of theoutput voltage with respect to a designated voltage is constant.

Another object of the present invention is to provide a voltageconversion method of converting a direct current voltage into an outputvoltage such that the follow-up property of the output voltage withrespect to a designated voltage is constant.

The further object of the present invention is to provide acomputer-readable recording medium with a program recorded thereon toallow a computer to execute control of voltage conversion converting adirect current voltage into an output voltage such that the follow-upproperty of the output voltage with respect to a designated voltage isconstant.

According to the present invention, a voltage conversion apparatusconverts a direct current voltage from a DC power supply into an outputvoltage such that the output voltage is equal to a designated voltage,and includes a voltage converter, detection means, and control means.

The voltage converter alters the voltage level of the direct currentvoltage to provide an output voltage. The detection means detects theoutput voltage from the voltage converter. The control means controlsthe voltage converter such that the follow-up property of the outputvoltage to the designated voltage in feedback control matches thereference property, and the output voltage is equal to the designatedvoltage, based on the detected output voltage and designated voltage.

Preferably, the voltage converter includes a chopper circuit. Thecontrol means includes a feedback voltage control value calculationunit, a duty ratio calculation unit, and a switching signal generationunit. The feedback voltage control value calculation unit detects adifference between the output voltage and the designated voltage,determines the control gain in feedback control in accordance with thedetected difference, and calculates a feedback voltage control value infeedback control such that the follow-up property is equal to thereference property based on the determined control gain, the outputvoltage, and the difference. The duty ratio calculation unit calculatesthe switching duty ratio in the chopper circuit based on the calculatedfeedback voltage control value. The switching signal generation unitgenerates a switching signal having a switching duty ratio calculated bythe duty ratio calculation unit to provide the generated switchingsignal to the chopper circuit.

Preferably, the feedback voltage control value calculation unitcalculates the feedback designated voltage by correcting the feedbackpreliminary voltage control value calculated using a control gain suchthat the follow-up property is equal to the reference property.

Preferably, the feedback voltage control value calculation unit includesa subtracter, a gain determination unit, a computing element, and acorrector.

The subtracter calculates the difference between the output voltage andthe designated voltage. The gain determination unit determines thecontrol gain based on the difference. The computing element calculatesthe feedback preliminary voltage control based on the determined controlgain. The corrector corrects the feedback preliminary voltage control byconverting the output voltage into the reference voltage where thefollow-up property is equal to the reference property and provides afeedback voltage control value.

Preferably, the corrector calculates the ratio of the reference voltageto the output voltage, and corrects the feedback preliminary voltagecontrol value by multiplying the calculated result by the feedbackpreliminary voltage control value.

Preferably, the feedback voltage control value calculation unitcalculates the feedback voltage control value by correcting thedifference such that the follow-up property is equal to the referenceproperty.

Preferably, the feedback voltage control value calculation unit includesa subtracter, a corrector, a gain determination unit, and a computingelement.

The subtracter calculates the difference between the output voltage andthe designated voltage. The corrector corrects the difference such thatthe follow-up property is equal to the reference property. The gaindetermination unit determines the control gain based on the difference.The computing element calculates the feedback voltage control valuebased on the determined control gain and corrected difference.

Preferably, the corrector corrects the difference by converting theoutput voltage into the reference voltage where the follow-up propertyis equal to the reference property.

Preferably, the corrector calculates the ratio of the reference voltageto the output voltage, and corrects the difference by multiplying thecalculated result by a difference.

Preferably, the voltage converter includes a chopper circuit. Thecontrol means includes a feedback voltage control value calculationunit, a duty ratio calculation unit, and a switching signal generationunit.

The feedback voltage control value calculation unit detects thedifference between the output voltage and the designated voltage,determines the control gain in feedback control in accordance with thedetected difference, and calculates the feedback preliminary voltagecontrol value in feedback control based on the determined control gain,the output voltage, and the difference. The duty ratio calculation unitcalculates a switching duty ratio of the chopper circuit such that thefollow-up property is equal to the reference property based on thecalculated feedback preliminary voltage control value and outputvoltage. The switching signal generation unit generates a switchingsignal having a switching duty ratio calculated by the duty ratiocalculation unit, and provides the generated switching signal to thechopper circuit.

Preferably, the duty ratio calculation unit calculates the switchingduty ratio by correcting the preliminary duty ratio calculated using thefeedback preliminary voltage control value such that the follow-upproperty is equal to the reference property.

Preferably, the duty ratio calculation unit includes a computing elementand a corrector.

The computing element calculates a preliminary duty ratio in accordancewith the feedback preliminary voltage control value. The correctorcorrects the preliminary duty ratio such that the follow-up property isequal to the reference property.

Preferably, the corrector corrects the preliminary duty ratio byconverting the output voltage into the reference voltage where thefollow-up property is equal to the reference property.

Preferably, the corrector calculates the ratio of the reference voltageto the output voltage, and corrects the preliminary duty ratio bymultiplying the calculated result by the preliminary duty ratio.

According to the present invention, a voltage conversion method effectsfeedback control such that the output voltage is equal to a designatedvoltage, and converts a direct current voltage from a DC power supplyinto an output voltage; the method including: a first step of detectingthe output voltage; a second step of detecting a difference between adesignated voltage and the output voltage; a third step of determining acontrol gain in accordance with the detected difference; and a fourthstep of converting the direct current voltage into an output voltagesuch that the follow-up property of the output voltage with respect tothe designated voltage in feedback control matches the referenceproperty, and the output voltage is equal to the designated voltage,based on the determined control gain, the detected difference and thedetected output voltage.

Preferably, the direct current voltage is converted into an outputvoltage by a chopper circuit. The fourth step includes a first substepof calculating a feedback voltage control value that causes thefollow-up property in feedback control to match the reference propertybased on the control gain, difference, and output voltage, a secondsubstep of calculating a switching duty ratio of the chopper circuitusing the feedback voltage control value, and a third substep ofcontrolling the chopper circuit such that the output voltage is equal tothe designated voltage, based on the switching duty ratio.

Preferably, the first substep includes the step of calculating afeedback preliminary voltage control value in feedback control based onthe control gain and difference, and the step of calculating a feedbackvoltage control value by correcting the feedback preliminary voltagecontrol value using the output voltage.

Preferably, the step of calculating a feedback voltage control valueincludes the step of calculating a conversion ratio for conversion ofthe output voltage into a reference voltage where the follow-up propertyis equal to the reference property, and the step of multiplying thefeedback preliminary voltage control value by the conversion ratio tocalculate a feedback voltage control value.

Preferably, the first substep includes the step of calculating acorrection difference where the follow-up property is equal to thereference property by correcting the difference using the outputvoltage, and the step of calculating the feedback voltage control valuebased on the control gain and the correction difference.

Preferably, the step of calculating a correction difference includes thestep of calculating a conversion ratio for conversion of the outputvoltage into a reference voltage where the follow-up property is equalto the reference property, and the step of multiplying the difference bythe conversion ratio to calculate a correction difference.

Preferably, the direct current voltage is converted into the outputvoltage by a chopper circuit. The fourth step includes a first substepof calculating a feedback preliminary voltage control value in feedbackcontrol based on the control gain and difference, a second substep ofcalculating a preliminary switching duty ratio of the chopper circuitbased on the feedback preliminary voltage control value, a third substepof calculating a switching duty ratio where the follow-up property isequal to the reference property by correcting the preliminary switchingduty ratio using the output voltage, and a fourth substep of controllingthe chopper circuit such that the output voltage is equal to thedesignated voltage based on the switching duty ratio.

Preferably, the third substep includes the step of calculating theconversion ratio required for conversion of the output voltage into areference voltage where the follow-up property is equal to the referenceproperty, and the step of multiplying the preliminary switching dutyratio by the conversion ratio to calculate a switching duty ratio.

In accordance with the present invention, a computer-readable recordingmedium with a program recorded thereon to allow a computer to executevoltage conversion control of effecting feedback control such that anoutput voltage is equal to a designated voltage, and converting a directcurrent voltage from a DC power supply into an output voltage; causes acomputer to execute: a first step of detecting the output voltage; asecond step of detecting a difference between a designated voltage andthe output voltage; a third step of determining a control gain inaccordance with the detected difference; and a fourth step of convertingthe direct current voltage into an output voltage such that thefollow-up property of the output voltage with respect to the designatedvoltage in feedback control matches the reference property, and theoutput voltage is equal to the designated voltage, based on thedetermined control gain, the detected difference and the detected outputvoltage.

Preferably, the direct current voltage is converted into an outputvoltage by a chopper circuit. In the program recorded on acomputer-readable recording medium, the fourth step includes a firstsubstep of calculating a feedback voltage control value that causes thefollow-up property in feedback control to match the reference propertybased on the control gain, difference, and output voltage, a secondsubstep of calculating a switching duty ratio of the chopper circuitusing the feedback voltage control value, and a third substep ofcontrolling the chopper circuit such that the output voltage is equal tothe designated voltage based on the switching duty ratio.

Preferably in the program recorded on a computer-readable recordingmedium, the first substep includes the step of calculating a feedbackpreliminary voltage control value in feedback control based on thecontrol gain and difference, and the step of calculating a feedbackvoltage control value by correcting the feedback preliminary voltagecontrol value using the output voltage.

Preferably in the program recorded on a computer-readable recordingmedium, the step of calculating a feedback voltage control valueincludes the step of calculating a conversion ratio required forconversion of the output voltage into a reference voltage where thefollow-up property is equal to the reference property, and the step ofmultiplying the feedback preliminary voltage control value by theconversion ratio to calculate a feedback voltage control value.

Preferably in the program recorded on a computer-readable recordingmedium, the first substep includes the step of calculating a correctiondifference where the follow-up property is equal to the referenceproperty by correcting the difference using the output voltage, and thestep of calculating the feedback voltage control value based on thecontrol gain and the correction difference.

Preferably in the program recorded on a computer-readable recordingmedium, the step of calculating a correction difference includes thestep of calculating a conversion ratio for conversion of the outputvoltage into a reference voltage where the follow-up property is equalto the reference property, and the step of multiplying the difference bythe conversion ratio to calculate a correction difference.

Preferably, the direct current voltage is converted into the outputvoltage by a chopper circuit. In the program recorded on acomputer-readable recording medium, the fourth step includes a firstsubstep of calculating a feedback preliminary voltage control value infeedback control based on the control gain and difference, a secondsubstep of calculating a preliminary switching duty ratio of the choppercircuit based on the feedback preliminary voltage control value, a thirdsubstep of calculating a switching duty ratio where the follow-upproperty is equal to the reference property by correcting thepreliminary switching duty ratio using the output voltage, and a fourthsubstep of controlling the chopper circuit such that the output voltageis equal to the designated voltage based on the switching duty ratio.

Preferably in the program recorded on a computer-readable recordingmedium, the third substep includes the step of calculating theconversion ratio required for conversion of the output voltage into areference voltage where the follow-up property is equal to the referenceproperty, and the step of multiplying the preliminary switching dutyratio by the conversion ratio to calculate a switching duty ratio.

In accordance with the present invention, the direct current voltagefrom a DC power supply can be converted into the output voltage with thefollow-up property of the output voltage to the designated voltage infeedback control kept constant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a motor driver including avoltage conversion apparatus according to a first embodiment.

FIG. 2 is a functional block diagram of a control device in FIG. 1.

FIG. 3 is a functional block diagram to describe the function of a motortorque control means in FIG. 2.

FIG. 4 is a functional block diagram to describe the function of afeedback voltage control value calculation unit and a duty ratioconverter in FIG. 3.

FIG. 5 is a diagram representing the relationship between feedbackvoltage control and the output voltage of a voltage-up converter.

FIG. 6 is a diagram to describe the duty ratio generated by a duty ratiocalculation unit in FIG. 4.

FIG. 7 is a timing chart of a signal generated by a duty ratio converterin FIG. 3.

FIG. 8 is a timing chart of a control pattern.

FIG. 9 is a flow chart to describe an operation of voltage conversioncontrol in the first embodiment.

FIG. 10 is a schematic block diagram of a motor driver including avoltage conversion apparatus according to a second embodiment.

FIG. 11 is a functional block diagram of a control device in FIG. 9.

FIG. 12 is a functional block diagram to describe the function of amotor torque control means in FIG. 10.

FIG. 13 is a functional block diagram to describe the function of afeedback voltage control value calculation unit and duty ratio converterin FIG. 11.

FIG. 14 is a flow chart to describe an operation of voltage conversioncontrol in the second embodiment.

FIG. 15 is a schematic block diagram of a motor driver including avoltage conversion apparatus according to a third embodiment.

FIG. 16 is a functional block diagram of a control device in FIG. 14.

FIG. 17 is a functional block diagram to describe a function of a motortorque control means in FIG. 15.

FIG. 18 is a functional block diagram to describe a function of afeedback voltage control value calculation unit and duty ratio converterin FIG. 16.

FIG. 19 is a flow chart to describe an operation of voltage conversioncontrol according to a third embodiment.

FIG. 20 is a schematic block diagram of a motor driver including avoltage conversion apparatus according to a fourth embodiment.

FIG. 21 is a functional block diagram of a control device in FIG. 19.

FIG. 22 is a functional block diagram to describe the function of amotor torque control means in FIG. 20.

FIG. 23 is a schematic block diagram of a conventional motor driver.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detailhereinafter with reference to the drawings. In the drawings, the same orcorresponding components have the same reference characters allotted,and the description thereof will not be repeated.

First Embodiment

Referring to FIG. 1, a motor driver 100 including a voltage conversionapparatus according to a first embodiment of the present inventionincludes a DC power supply B, voltage sensors 10 and 13, system relaysSR1 and SR2, capacitors C1 and C2, a voltage-up converter 12, aninverter 14, a current sensor 24, and a control device 30.

An alternating current motor M1 is a drive motor to generate torque todrive the driving wheel of a hybrid vehicle or electric vehicle.Alternatively, the motor may be incorporated in a hybrid vehicle withthe capability of a generator driven by an engine, and operating as amotor for the engine to allow, for example, engine starting.

Voltage-up converter 12 includes a reactor L1, NPN transistors Q1 andQ2, and diodes D1 and D2. Reactor L1 has one end connected to a powersupply line of DC power supply B, and its other end connected at anintermediate point of NPN transistor Q1 and NPN transistor Q2, i.e.,between the emitter of NPN transistor Q1 and the collector of NPNtransistor Q2. NPN transistors Q1 and Q2 are connected in series betweena power supply line and a ground line. NPN transistor Q1 has itscollector connected to the power supply line, whereas NPN transistor Q2has its emitter connected to the ground line. Diodes D1 and D2 flowingcurrent from the emitter side to the collector side are connectedbetween the collectors and emitters of NPN transistors Q1 and Q2,respectively.

Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phasearm 17 U-phase arm 15, V-phase arm 16, and W-phase arm 17 are connectedin parallel between the power supply line and the ground line.

U-phase arm 15 is constituted of NPN transistors Q3 and Q4 connected inseries. V-phase arm 16 is constituted of NPN transistors Q5 and Q6connected in series. W-phase arm 17 is constituted of NPN transistors Q7and Q8 connected in series. Diodes D3-D8 are connected betweenrespective collectors and emitters of NPN transistors Q3-Q8,respectively, to allow a current flow from the emitter side to thecollector side.

Each of the phase arms has an intermediate point connected to respectiveends of phase coils of alternating current motor M1. Specifically,alternating current motor M1 is a three-phase permanent magnet motorwith respective one ends of the three coils of the U, V, and W-phaseconnected in common at the center. The other end of the U-phase coil isconnected to the intermediate point between NPN transistors Q3 and Q4.The other end of the V-phase coil is connected to the intermediate pointbetween NPN transistors Q5 and Q6. The other end of the W-phase coil isconnected to the intermediate point between NPN transistors Q7 and Q8.

DC power supply B is formed of a nickel-hydrogen or lithium-ionsecondary battery. Voltage sensor 10 detects a direct current voltage Vbfrom DC power supply B to output the detected voltage Vb to controldevice 30. System relays SR1 and SR2 are turned on by a signal SE fromcontrol device 30. Capacitor C1 smoothes a DC voltage supplied from DCpower supply B to provide the smoothed DC voltage to voltage-upconverter 12.

Voltage-up converter 12 boosts the DC voltage from capacitor C1 tosupply the boosted voltage to-capacitor C2. More specifically,voltage-up converter 12 receives a signal PWU from control device 30 toboost and supply to capacitor C2 the DC voltage in response to a periodin which NPN transistor Q2 is turned on by signal PWU.

Further, voltage-up converter 12 receives a signal PWD from controldevice 30 to down-convert a DC voltage supplied from inverter 14 viacapacitor C2, whereby DC power supply B is charged. It is to be notedthat a circuit configuration in which only the boosting function iseffected may be applied.

Capacitor C2 smoothes the DC voltage from voltage-up converter 12 tosupply the smoothed DC voltage to inverter 14. Voltage sensor 13 detectsthe voltage across capacitor C2, i.e., output voltage Vm from voltage-upconverter 12 (corresponding to the input voltage to inverter 14; thesame applies hereinafter) and provides the detected output voltage Vm tocontrol device 30.

Inverter 14 receives the DC voltage from capacitor C2 to convert the DCvoltage into an AC voltage based on a signal PWMI from control device30, whereby alternating current motor M1 is driven. Then, alternatingcurrent motor M1 is driven to generate torque designated by a torquecontrol value TR. In regenerative braking of a hybrid or electricvehicle including motor driver 100, inverter 14 converts an AC voltagegenerated by alternating current motor M1 into a DC voltage according toa signal PWMC from control device 30 and supplies the converted DCvoltage to voltage-up converter 12 via capacitor C2. As used herein,“regenerative braking” includes braking which is caused when a driver ofa hybrid or electric vehicle depresses the foot brake and which isaccompanied by regenerative power generation as well as deceleration (orstopping of acceleration) of the vehicle by releasing the accelerationpedal in driving without operating the foot brake, which is alsoaccompanied by regenerative power generation.

Current sensor 24 detects a motor current MCRT flowing to alternatingcurrent motor M1 to output the detected motor current MCRT to controldevice 30.

Control device 30 generates a signal PWU required to drive voltage-upconverter 12 and a signal PWMI required to drive inverter 14 by a methodthat will be described afterwards, and provides the generated signalsPWU and PWMI to voltage-up converter 12 and inverter 14, respectively,based on a torque control value TR and a motor rotation number MRNapplied from an external ECU (Electrical Control Unit), a direct currentvoltage Vb from voltage sensor 10, an output voltage Vm from voltagesensor 13, and a motor current MCRT from current sensor 24.

Signal PWU is a signal to drive voltage-up converter 12 when voltage-upconverter 12 converts the direct current voltage from capacitor C1 intooutput voltage Vm. Control device 30 effects feedback control of outputvoltage Vm when voltage-up converter 12 is to convert direct currentvoltage Vb into output voltage Vm, and generates signal PWU required todrive voltage-up converter 12 such that output voltage Vm is equal to adesignated voltage control value Vdccom. The method of generating signalPWU will be described afterwards.

Control device 30 responds to a signal indicating that the hybridvehicle or electric vehicle attains a regenerative braking mode from theexternal ECU to generate and provide to inverter 14 a signal PWMCrequired to convert the alternating voltage generated by alternatingcurrent motor M1 into a direct current voltage. At this stage, NPNtransistors Q4, Q6 and Q8 of inverter 14 are switched under control ofsignal PWMC. Specifically, NPN transistors Q6 and Q8 are turned on, NPNtransistors Q4 and Q8 are turned on, and NPN transistors Q4 and Q6 areturned on when electric power is generated by the U-phase, the V-phase,and the W-phase, respectively, of alternating current motor M1.Accordingly, inverter 14 converts the alternating voltage generated byalternating current motor M1 into a direct current voltage and suppliesthe same to voltage-up converter 12.

Further, control device 30 also responds to a signal indicating that thehybrid vehicle or electric vehicle has entered a regenerative brakingmode from the external ECU to generate signal PWD required todown-convert the direct current voltage supplied from inverter 14, andprovides the generated signal PWD to voltage-up converter 12.Accordingly, the alternating voltage generated by alternating currentmotor M1 is converted into a direct current voltage, and thendown-converted to be supplied to DC power supply B.

Control device 30 also generates signal SE required to turn on systemrelays SR1 and SR2, and provides the generated signal SE to systemrelays SR1 and SR2.

FIG. 2 is a functional block diagram of control device 30. Referring toFIG. 2, control device 30 includes a motor torque control means 301, anda voltage conversion control means 302. Motor torque control means 301generates, during driving of alternating current motor M1, signalPWU-required to turn on/off NPN transistors Q1 and Q2 of voltage-upconverter 12 by a method as will be described afterwards, and signalPMWI required to turn on/off NPN transistors Q3-Q8 of inverter 14, andprovides the generated signals PWU and PWMI to voltage-up converter 12and inverter 14, respectively, based on a torque control value TR (thedegree of depressing the acceleration peddle of a vehicle; torquecontrol value to be applied to the motor is calculated taking intoaccount the operational status of the engine in a hybrid vehicle),direct current voltage Vb from DC power supply B, motor current MCRT,motor rotation number MRN, and output voltage Vm of voltage-up converter12.

When in a regenerative braking mode, voltage conversion control means302 receives a signal RGE indicating that the hybrid vehicle or electricvehicle has entered a regenerative braking mode from the external ECU togenerate and provide to inverter 14 a signal PWMC required to convertthe alternating voltage generated by alternating current motor M1 into adirect current voltage.

Voltage conversion generation means 302 also generates and provides tovoltage-up converter 12 a signal PWD required to down-convert the directcurrent voltage supplied from inverter 14 in response to reception ofsignal RGE from the external ECU in a regenerative braking mode. Assuch, voltage-up converter 12 has the capability of a bidirectionalconverter since the direct current voltage can be down-convert by asignal PWD directed thereto.

FIG. 3 is a functional block diagram of motor torque control means 301.Referring to FIG. 3, motor torque control means 301 includes a motorcontrol phase voltage calculation unit 40, a PWM signal converter 42 forthe inverter, an inverter input voltage control value calculation unit50, a feedback voltage control value calculation unit 52, and a dutyratio converter 54.

Motor control phase voltage calculation unit 40 receives output voltageVm of voltage-up converter 12, i.e. the input voltage to inverter 14from voltage sensor 13, motor current MCRT flowing through each phase ofalternating current motor M1 from current sensor 24, and torque controlvalue TR from the external ECU. Motor control phase voltage calculationunit 40 calculates the voltage to be applied to the coil of each phaseof alternating current motor M1 based on these input signals to supplythe calculated result to PWM signal converter 42.

PWM signal converter 42 actually generates signal PWMI that turns on/offeach of NPN transistors Q3-Q8 of inverter 14 in accordance with thecalculated result from motor control phase voltage calculation unit 40to provide the generated signal PWMI to each of NPN transistors Q3-Q8 ofinverter 14.

Accordingly, each of NPN transistors Q3-Q8 has its switching controlled,whereby the current to be conducted to each phase of alternating currentmotor M1 is adjusted such that alternating current motor M1 outputs thedesignated torque. Thus, motor driving current is controlled so that amotor torque corresponding to torque control value TR is output.

Inverter input voltage control value calculation unit 50 calculates theoptimum value (target value) of the inverter input voltage based ontorque control value TR and motor rotation number MRN, i.e. calculatesvoltage control value Vdccom and provides the calculated voltage controlvalue Vdccom to feedback voltage control value calculation unit 52.

Feedback voltage control value calculation unit 52 calculates a feedbackvoltage control value Vdccom_fb by a method that will be describedafterwards based on output voltage Vm of voltage-up converter 12 fromvoltage sensor 13 and voltage control value Vdccom from inverter inputvoltage control value calculation unit 50 to provide the calculatedfeedback voltage control value Vdccom_fb to duty ratio converter 54.Feedback voltage control value calculation unit 52 calculates acompensation ratio Rcom based on voltage control value Vdccom and abattery voltage Vb from voltage sensor 10 to provide the calculatedcompensation ratio Rcom to duty ratio converter 54.

Compensation ratio Rcom is used to incorporate direct current voltage Vboutput from DC power supply into the feedback control of output voltageVm. Specifically, the duty ratio for turning on/off NPN transistors Q1and Q2 of voltage-up converter 12 is determined in view of directcurrent voltage Vb since voltage-up converter 12 is directed toconverting direct current voltage Vb into voltage control value Vdccom.

Duty ratio converter 54 calculates a duty ratio for setting outputvoltage Vm from voltage sensor 13 to feedback voltage control valueVdccom_fb from feedback voltage control value calculation unit 52 basedon battery voltage Vb from voltage sensor 10, feedback voltage controlvalue Vdccom_fb from feedback voltage control value calculation unit 52,and compensation ratio Rcom, and generates signal PWU required to turnon/off NPN transistors Q1 and Q2 of voltage-up converter 12 based on thecalculated duty ratio. Duty ratio converter 54 provides the generatedsignal PWU to NPN transistors Q1 and Q2 of voltage-up converter 12.

Since a greater amount of electric power is accumulated by reactor L1 byincreasing the on-duty of NPN transistor Q2 located at the lower side ofvoltage-up converter 12, a higher voltage output can be obtained. Incontrast, the voltage of the power supply line is reduced by increasingthe on-duty of NPN transistor Q1 located at the upper side. Therefore,by controlling the duty ratio of NPN transistors Q1 and Q2, the voltageof the power supply line can be adjusted to an arbitrary level equal toor greater than the output voltage of DC power supply B.

Referring to FIG. 4, feedback voltage control value calculation unit 52includes a subtracter 521, a gain determination unit 522, a PIcontroller 523, a corrector 524, and a forward compensator 525.Subtracter 521 receives voltage control value Vdccom from inverter inputvoltage control value calculation unit 50 and output voltage Vm fromvoltage sensor 13 to subtract voltage control value Vdccom from outputvoltage Vm. Subtracter 521 provides the subtracted result to gaindetermination unit 522 and PI controller 523 as a difference ΔVdc.

Gain determination unit 522 determines a PI control gain in accordancewith difference ΔVdc from subtracter 521. In other words, gaindetermination unit 522 determines a proportional gain PG and anintegration gain IG in accordance with difference ΔVdc. Gaindetermination unit 522 provides the determined PI control gain to PIcontroller 523.

PI controller 523 calculates a feedback preliminary voltage controlvalue Vdccom_fb_pr based on the PI control gain from gain determinationunit 522 and difference ΔVdc from subtracter 521. Specifically, PIcontroller 523 calculates feedback preliminary voltage control valueVdccom_fb_pr by inserting proportional gain PG from gain determinationunit 522 and integration gain IG received from gain determination unit522, and difference ΔVdc received from subtracter 521 into the followingequation.Vdccom _(—) fb _(—) pr=PG×ΔVdc+IG×ΣVdc  (1)

Corrector 524 receives feedback preliminary voltage control valueVdccom_fb_pr from PI controller 523 and output voltage Vm from voltagesensor 13 to correct feedback preliminary voltage control valueVdccom_fb_pr based on the following equation to calculate feedbackvoltage control value Vdccom_fb. $\begin{matrix}{{Vdccom\_ fb} = {{Vdccom\_ fb}{\_ pr} \times \frac{Vstd}{Vm}}} & (2)\end{matrix}$where Vstd represents the reference voltage. Reference voltage Vstd isthe output voltage of voltage-up converter 12 where the follow-upproperty of output voltage Vm with respect to voltage control valueVdccom is equal to the reference property.

By dividing reference voltage Vstd by output voltage Vm, corrector 524calculates the conversion ratio required to convert output voltage Vminto reference voltage Vstd where the follow-up property of outputvoltage Vm to voltage control value Vdccom is equal to the referenceproperty. Then, corrector 524 multiplies the calculated conversion ratioby feedback preliminary voltage control value Vdccom_fg_pr to calculatefeedback voltage control value Vdccom_fb where the follow-up property ofoutput voltage Vm to voltage control value Vdccom is equal to thereference property.

Forward compensator 525 receives voltage control value Vdccom frominverter input voltage control value calculation unit 50 and batteryvoltage Vb from voltage sensor 10 to calculate compensation ratio Rcomby the following equation. $\begin{matrix}{{Rcom} = \frac{Vb}{Vdccom}} & (3)\end{matrix}$

Then, forward compensator 525 furthermore calculates a compensationratio 1−Rcom using compensation ratio Rcom to provide compensation ratioRcom and compensation ratio 1−Rcom to duty ratio converter 54.

Duty ratio converter 54 includes a duty ratio calculation unit 541, anadder 542, and a PWM signal converter 543. Duty ratio calculation unit541 calculates a duty ratio required to set output voltage Vm fromvoltage sensor 13 to feedback voltage control value Vdccom_fb based onbattery voltage Vb from voltage sensor 10 and feedback voltage controlvalue Vdccom_fb from corrector 524.

Adder 542 receives the duty ratio from duty ratio calculation unit 541and the compensation ratios Rcom and 1−Rcom from forward compensator 525to calculate two compensation duty ratios by adding respectivecompensation ratios Rcom and 1−Rcom to the duty ratio. Adder 524provides the two compensation duty ratios to PWM signal converter 543.

PWM signal converter 543 generates signal PWU required to turn on/offNPN transistors Q1 and Q2 of voltage-up converter 12 based on the twocompensation duty ratios from adder 542. Specifically, PWM signalconverter 543 generates signal PWU that determines the on-duties D1 andD2 of NPN transistors Q1 and Q2 of voltage-up converter 12 by thefollowing equations (4) and (5), where the on-duty output from dutyratio calculation unit 541 is D0.D 1=D 0+Rcom  (4)D 2=D 0+1−Rcom  (5)

PWM signal conversion unit 543 provides the generated signal PWU to NPNtransistors Q1 and Q2 of voltage-up converter 12. NPN transistors Q1 andQ2 of voltage-up converter 12 are turned on/off in response to signalPWU. Accordingly, voltage-up converter 12 converts direct currentvoltage Vb into output voltage Vm such that output voltage Vm is equalto voltage control value Vdccom. In this case, the follow-up property ofoutput voltage Vm with respect to voltage control value Vdccom matchesthe reference property.

Thus, motor torque control means 301 of control device 30 receivestorque control value TR from the external ECU to effect feedback controlof voltage conversion in voltage-up converter 12 converting directcurrent voltage Vb into output voltage Vm such that output voltage Vm ofvoltage-up converter 12 is equal to voltage control value Vdccomcalculated based on torque control value TR, and controls inverter 14such that alternating current motor M1 generates the torque of torquecontrol value TR. Accordingly, alternating current motor M1 generatesthe torque designated by torque control value TR.

As described above, corrector 524 corrects feedback preliminary voltagecontrol value Vdccom_fb_pr output from PI controller 523 based onequation (2). The relationship of equation (2) corresponds to curve k1in FIG. 5.

Referring to FIG. 5, when output voltage Vm of voltage-up converter 12is equal to reference voltage Vstd, feedback voltage control valueVdccom_fb is equal to feedback voltage control value Vdccom_fb0(=Vdccom_fb_pr). When output voltage Vm is higher than reference voltageVstd, feedback voltage control value Vdccom_fb is equal to feedbackvoltage control value Vdccom_fb1. When output voltage Vm is lower thanreference voltage Vstd, feedback voltage control value Vdccom_fb isequal to feedback voltage control value Vdccom_fb2.

Referring to FIG. 6, duty ratio calculation unit 541 calculates a dutyratio DR0 where the on-duty is D00 (<1) based on feedback voltagecontrol value Vdccom_fb0 when output voltage Vm is equal to referencevoltage Vstd. When output voltage Vm is higher than reference voltageVstd, duty ratio calculation unit 541 calculates a duty ratio DR1 wherethe on-duty is D01 (<D00) based on feedback voltage control valueVdccom_fb1. When output voltage Vm is lower than reference voltage Vstd,duty ratio calculation unit 541 calculates a duty ratio DR2 where theon-duty is D02 (D00<D02<1) based on feedback voltage control valueVdccom_fb2.

When output voltage Vm is equal to reference voltage Vstd, adder 542adds compensation ratio Rcom to duty ratio DR0 to provide compensationduty ratio DR0U to PWM signal converter 543, and adds compensation ratio1−Rcom to duty ratio DR0 to provide compensation duty ratio DR0L to PWMsignal converter 543.

When output voltage Vm is higher than reference voltage Vstd, adder 542adds compensation ratio Rcom to duty ratio DR1 to provide compensationduty ratio DR1U to PWM signal converter 543, and adds compensation ratio1−Rcom to duty ratio DR1 to provide compensation duty ratio DR1L to PWMsignal converter 543.

When output voltage Vm is lower-than reference voltage Vstd, adder 542adds compensation ratio Rcom to duty ratio DR2 to provide compensationratio duty ratio DR2U to PWM signal converter 543, and adds compensationratio 1−Rcom to duty ratio DR0 to provide compensation ratio duty rationDR2L to PWM signal converter 543.

Referring to FIG. 7, when output voltage Vm is equal to referencevoltage Vstd, PWM signal converter 543 generates signals PWU0U and PWU0Lbased on duty ratios DR0U and DR0L to provide a signal PWU0 constitutedof signals PWU0U and PWU0L to voltage-up converter 12. When outputvoltage Vm is higher than reference voltage Vstd, PWM signal converter543 generates signals PWU1U and PWU1L based on duty ratios DR1U and DR1Lto output a signal PWU1 constituted of signals PWU1U and PWU1L tovoltage-up converter 12. When output voltage Vm is lower than referencevoltage Vstd, PWM signal converter 543 generates signals PWU2U and PWU2Lbased on duty ratios DR2U and DR2L to provide a signal PWU2 constitutedof signals PWU2U and PWU2L to voltage-up converter 12.

Signals PWU0U, PWU1U and PWU2U are signals for turning on/off NPNtransistor Q1 of voltage-up converter 12, whereas PWU0L, PWU1L and PWU2Lare signals for turning on/off NPN transistor Q2 of voltage-up converter12.

FIG. 8 represents the follow-up property of output voltage Vm withrespect to feedback voltage control value Vdccom_fb0 in feedback controlwhen NPN transistors Q1 and Q2 of voltage-up converter 12 are turnedon/off using signals PWU0, PWU1 and PWU2 shown in FIG. 7.

Referring to FIG. 8, output voltage Vm follows feedback voltage controlvalue Vdccom_fb0 as in pattern 1 when output voltage Vm matchesreference voltage Vstd. Specifically, output voltage Vm starts from apoint A at timing t0 to cross feedback voltage control value Vdccom_fb0at timing t1, and then follows feedback voltage control value Vdccom_fb0in accordance with a curve k2. The follow up property represented bycurve k2 is referred to as the “reference property”.

When output voltage Vm is higher than reference voltage Vstd, outputvoltage Vm follows feedback voltage control value Vdccom_fb0 as inpattern 2. Specifically, output voltage Vm starts from a point Bindicating a voltage that is higher than reference voltage Vstd, risesmore gentle than in pattern 1 since the on-duty of NPN transistor Q2(DO1+1−Rcom) is smaller than that of pattern 1 (DOO+1−Rcom), and crossesfeedback voltage control value Vdccom_fb0 at timing t1. Then, outputvoltage Vm follows feedback voltage control value Vdccom_fb0 inaccordance with curve k2 as in pattern 1.

In this context, output voltage Vm follows feedback voltage controlvalue Vdccom_fb0 in accordance with curve k3 when correction of feedbackpreliminary voltage control value Vdccom_fb_pr is not conducted bycorrector 524. Specifically, output voltage Vm rises at the same speedas in pattern 1, and then crosses feedback voltage control valueVdccom_fb0 at a timing t2 earlier than timing t1 to follow feedbackvoltage control value Vdccom_fb0 thereafter.

By correcting difference ΔVdc by a conversion ratio Vstd<1, the followup property (represented by curve k3) deviating from the referenceproperty (represented by curve k2) will match the reference property.

When output voltage Vm is lower than reference voltage Vstd, outputvoltage Vm follows feedback voltage control value Vdccom_fb0 as inpattern 3. Specifically, output voltage Vm starts from a point Cindicating a voltage that is of lower level than reference voltage Vstd,rises faster than in pattern I since the on-duty (D02+1−Rcom) of NPNtransistor Q2 is larger than that of pattern I (D00+1−Rcom), and crossesfeedback voltage control value Vdccom_fb0 at timing t1. Then, outputvoltage Vm follows feedback voltage control value Vdccom_fb0 inaccordance with curve k2 as in pattern 1.

In this context, output voltage Vm follows feedback voltage controlvalue Vdccom_fb0 in accordance with curve k4 when correction of feedbackpreliminary voltage control value Vdccorm_fb_pr is not conducted bycorrector 524. Specifically, output voltage Vm rises at a speedidentical to that of pattern 1, crosses feedback voltage control valueVdccom_fb0 at timing t3 later than timing t1, and then follows feedbackvoltage control value Vdccom_fb0 thereafter.

Thus, by correcting difference ΔVdc with a conversion ratio Vstd>1, thefollow-up property (represented by curve k4) deviated from the referenceproperty (represented by curve k2) will match the reference property.

Since feedback voltage control Vdccom_fb0 (=Vdccom_fb_pr) is adesignated voltage calculated for feedback control such that outputvoltage Vm is equal to output control value Vdccom, the follow-up ofoutput voltage Vm to feedback voltage control value Vdccom_fb0 is equalto the follow-up of output voltage Vm to voltage control value Vdccom.

Therefore, when output voltage Vm is not equal to reference voltageVstd, control is effected such that feedback preliminary voltage controlvalue Vdccom_fb_pr is corrected and the follow-up property of outputvoltage Vm with respect to output control value Vdccom is equal to thereference property.

Thus, by correcting feedback preliminary voltage control valueVdccom_fb_pr based on output voltage Vm, the follow-up property ofoutput voltage Vm with respect to voltage control value Vdccom can bekept constant even if output voltage Vm varies.

An operation of control in the voltage conversion of the direct currentvoltage into output voltage Vm at voltage-up converter 12 will bedescribed with reference to FIG. 9. Upon initiation of the operation,voltage sensor 10 detects direct current voltage Vb from DC power supplyB to provide the detected direct current voltage Vb to control device30. Voltage sensor 13 detects output voltage Vm of voltage-up converter12 to provide the detected output voltage Vm to control device 30 (stepS1).

At control device 30, subtracter 521 calculates a difference ΔVdcbetween output voltage Vm and voltage control value Vdccom to provide acalculated difference ΔVdc to gain determination unit 522 and PIcontroller 523 (step S2). Then, gain determination unit 522 determinesthe control gain constituted of proportional gain PG and integrationgain IG in accordance with difference ΔVdc (step S3).

PI controller 523 receives the control gain from gain determination unit522 and difference ΔVdc from subtracter 521 to insert proportional gainPG, integration gain IG and difference ΔVdc into equation (1) tocalculate feedback preliminary voltage control value Vdccom_fb_pr (stepS4).

Corrector 524 receives feedback preliminary voltage control valueVdccom_fb_pr from PI controller 523 and output voltage Vm from voltagesensor 13 to correct feedback preliminary voltage control valueVdccom_fb_pr in accordance with output voltage Vm based on equation (2)to calculate feedback voltage control value Vdccom_fb where thefollow-up property of output voltage Vm to voltage control value Vdccomis equal to the reference property. Then, corrector 524 provides thecalculated feedback voltage control value Vdccom_fb to duty ratiocalculation unit 541 (step S5).

Duty ratio calculation unit 541 calculates the duty ratio (any of DR0,DR1 and DR2) by the method set forth above based on feedback voltagecontrol value Vdccom_fb, and provides the calculated duty ratio to adder542 (S6).

Forward compensator 525 receives direct current voltage Vb from voltagesensor 10 and voltage control value Vdccom from inverter input voltagecontrol value calculation unit 50 to calculate and provide to adder 542compensation ratios Rcom and 1−Rcom based on equation (3).

Adder 542 adds compensation ratios Rcom and 1−Rcom from forwardcompensator 525 to the duty ratio from duty ratio calculation unit 541,and provides the compensation duty ratios to PWM signal converter 543.PWM signal converter 543 generates signal PWU based on the compensationduty ratios from adder 542 (step S7), and provides the generated signalPWU to voltage-up converter 12.

NPN transistors Q1 and Q2 of voltage-up converter 12 are turned on/offin accordance with signal PWU. Voltage-up converter 12 is controlledsuch that output voltage Vm is equal to voltage control value Vdccom(step S8). Then, the series of operations ends (step S9).

An operation of motor driver 100 will be described with reference toFIG. 1 again. Control device 30 responds to a torque control value TRinput from the external ECU to generate signal SE required to turn onsystem relays SR1 and SR2, and provides the generated signal SE tosystem relays SR1 and SR2. Control device 30 also generates and providesto voltage-up converter 12 and inverter 14 signals PWU and PWMI,respectively, required to control voltage-up converter 12 and inverter14 such that alternating current motor M1 generates torque control valueTR.

DC power supply B outputs direct current voltage Vb, and system relaysSR1 and SR2 supply direct current voltage Vb to capacitor C1. CapacitorC1 smoothes the supplied direct current voltage Vb to provide thesmoothed direct current voltage Vb to voltage-up converter 12.

Accordingly, NPN transistors Q1 and Q2 of voltage-up converter 12 areturned on/off in accordance with signal PWU from control device 30, anddirect current voltage Vb is converted into a voltage Vm to be suppliedto capacitor C2. Voltage sensor 13 detects output voltage Vm that is thevoltage across capacitor C2 to provide the detected output voltage Vm tocontrol device 30.

As described above, control device 30 calculates difference ΔVdc betweenvoltage control value Vdccom and output voltage Vm to determine the PIcontrol gain in accordance with the calculated difference ΔVdc. Controldevice 30 corrects the feedback preliminary voltage control valuecalculated using the determined PI control gain in accordance withoutput voltage Vm, and generates and provides to voltage-up converter 12signal PWU where the follow-up property of output voltage Vm withrespect to voltage control value Vdccom is equal to the referenceproperty. Accordingly, voltage-up converter 12 converts the directcurrent voltage into output voltage Vm such that output voltage Vm isequal to voltage control value Vdccom while achieving consistencybetween the follow-up property of output voltage Vm to voltage controlvalue Vdccom and the reference property.

Capacitor C2 smoothes and supplies to inverter 14 the direct currentvoltage from voltage-up converter 12. NPN transistors Q3-Q8 of inverter14 are turned on/off in accordance with signal PWMI from control device30. Inverter 14 converts the direct current voltage into the alternatingvoltage, and provides a predetermined alternating current to each of theU-phase, V-phase and W-phase of alternating current motor M1 such thatalternating current motor M1 generates the torque designated by torquecontrol value TR. Thus, alternating current motor M1 generates torquedesignated by torque control value TR.

When the hybrid vehicle or electric vehicle in which motor driver 100 isincorporated attains the regenerative braking mode, control device 30receives a signal indicating entry of the regenerative braking mode fromthe external ECU to generate and provide to inverter 14 and voltage-upconverter 12 signals PWMC and PWD, respectively.

Alternating current motor M1 generates the alternating voltage andsupplies the generated alternating current to inverter 14. Inverter 14converts the alternating voltage into the direct current voltage inaccordance with signal PWMC from control device 30, and supplies theconverted direct current voltage to voltage-up converter 12 viacapacitor C2.

Voltage-up converter 12 down-converts the direct current voltage inaccordance with signal PWD from control device 30 to supply thedown-converted voltage to DC power supply B, whereby DC power supply Bis charged.

Thus, in motor driver 100, direct current voltage Vb from DC powersupply B is converted into output voltage Vm such that the follow-upproperty of output voltage Vm of voltage-up converter 12 with respect tovoltage control value Vdccom is equal to the reference property, theconverted output voltage Vm is supplied to inverter 14 by a capacitorC2, and alternating current motor M1 is driven such that torquespecified by torque control value TR is generated. In the regenerativebraking mode, motor driver 100 is driven such that DC power supply B ischarged by the power generated by alternating current motor M1.

In the present invention, voltage-up converter 12 and also feedbackvoltage control value calculation unit 52 and duty ratio converter 54 ofcontrol device 30 constitute the “voltage conversion apparatus”.

In the present invention, feedback voltage control value calculationunit 52 and duty ratio converter 54 constitute the “control means” forcontrolling voltage-up converter 12 identified as a voltage converter.

PI controller 523 constitutes the “computing element” that calculatesfeedback preliminary voltage control value Vdccom_fb_pr.

The voltage conversion method of the present invention corresponds tothe voltage conversion method of converting the direct current voltageinto output voltage Vm under feedback control in accordance with theflow chart of FIG. 9.

The feedback control in feedback voltage control value calculation unit52 and duty ratio converter 54 is carried out actually by a CPU (CentralProcessing Unit). The CPU reads out a program including the respectivesteps in the flow chart of FIG. 9 from a ROM (Read Only Memory), andexecutes that program to control voltage conversion of the directcurrent voltage into output voltage Vm in accordance with the flow chartof FIG. 9. Therefore, the ROM corresponds to a computer (CPU) readablerecording medium on which the program including respective steps in theflow chart of FIG. 9 is recorded.

In accordance with the first embodiment, the voltage conversionapparatus includes control means for correcting the feedback preliminaryvoltage control value calculated based on the difference between anoutput voltage and a designated voltage to a feedback voltage controlvalue where the follow-up property of the output voltage to the voltagecontrol value is equal to the reference property, under feedback controlsuch that the output voltage that is a converted version of the directcurrent voltage from a DC power supply is equal to a voltage controlvalue. Therefore, the direct current voltage can be converted into anoutput voltage while keeping the follow-up property of the outputvoltage with respect to a voltage control value constant.

Second Embodiment

Referring to FIG. 10, a motor driver 100A including a voltage conversionapparatus according to a second embodiment of the present inventiondiffers from motor driver 100 only in that a control device 30A isprovided instead of control device 30 of motor driver 100.

Referring to FIG. 11, control device 30A differs from control device 30only in that a motor torque control means 301A is provided instead ofmotor torque control means 301 of control device 30.

Motor torque control means 301A generates and provides to inverter 14 asignal PWMI through a method identical to that of motor torque controlmeans 301, and generates and provides to voltage-up converter 12 asignal PWU for controlling NPN transistors Q1 and Q2 of voltage-upconverter 12 through a method that will be described afterwards.

Referring to FIG. 12, motor torque control means 301A differs from motortorque control means 301 only in that a feedback voltage control valuecalculation unit 52A is provided instead of feedback voltage controlvalue calculation unit 52 of motor torque control means 301.

Feedback voltage control value calculation unit 52A corrects differenceΔVdc between output voltage Vm and voltage control value Vdccom tocalculate feedback voltage control value Vdccom_fbv2 such that thefollow-up property of output voltage Vm to voltage control value Vdccomis equal to the reference property, based on voltage control valueVdccom from inverter input voltage control value calculation unit 50 andoutput voltage Vm from output sensor 13.

Referring to FIG. 13, feedback voltage control value calculation unit52A differs from feedback voltage control value calculation unit 52 onlyin that a corrector 524A is provided instead of corrector 524 offeedback voltage control value calculation unit 52, and a PI controller523A is provided instead of PI controller 523.

In feedback voltage control value calculation unit 52A, subtracter 521provides the calculated difference ΔVdc to gain determination unit 522,PI controller 523A and corrector 524A. Corrector 524A receivesdifference ΔVdc from subtracter 521 and output voltage Vm from voltagesensor 13 to correct difference ΔVdc in accordance with output voltageVm through the following equation. $\begin{matrix}{{\Delta\quad{Vdcc}} = {\Delta\quad{Vdc} \times \frac{Vstd}{Vm}}} & (6)\end{matrix}$

Then, corrector 524A provides the corrected correction difference ΔVdccto PI controller 523A.

Corrector 524A divides reference voltage Vstd by output voltage Vm tocalculate a conversion ratio required to convert output voltage Vm intoreference voltage Vstd where the follow-up property of output voltage Vmwith respect to voltage control value Vdccom is equal to the referenceproperty. Corrector 524A multiplies the calculated conversion ratio bydifference ΔVdc to calculate correction difference ΔVdcc required toobtain feedback voltage control value Vdccom_fbv2 where the follow-upproperty of output voltage Vm with respect to voltage control valueVdccom is equal to the reference property.

PI controller 523A receives the control gain from gain determinationunit 522 (proportional gain PG and integration gain IG), and correctiondifference ΔVdcc from corrector 524A to calculate feedback voltagecontrol value Vdccom_fbv2 by inserting proportional gain PG, integrationgain IG and correction difference ΔVdcc into the following equation.Vdccom _(—) fbv 2=PG×ΔVdcc+IG×ΣΔVdcc  (7)

PI controller 523A provides the calculated feedback voltage controlvalue Vdccom_fbv2 to duty ratio calculation unit 541. Inserting equation(1) into equation (2) yields: $\begin{matrix}{{Vdccom\_ fb} = {{{PG} \times \Delta\quad{Vdc} \times \frac{Vstd}{Vm}} + {{IG} \times {\Sigma\Delta}\quad{Vdc} \times \frac{Vstd}{Vm}}}} & (8)\end{matrix}$

Further, inserting equation (6) into equation (7) yields:$\begin{matrix}{{Vdccom\_ fb} = {{{PG} \times \Delta\quad{Vdc} \times \frac{Vstd}{Vm}} + {{IG} \times {\Sigma\Delta}\quad{Vdc} \times \frac{Vstd}{Vm}}}} & (9)\end{matrix}$

Accordingly, feedback voltage control value Vdccom_fbv2 output fromfeedback voltage control value calculation unit 52A matches feedbackvoltage control value Vdccom_fb output from feedback voltage controlvalue calculation unit 52 in the first embodiment.

In the first embodiment, feedback voltage control value calculation unit52 calculates feedback preliminary voltage control value Vdccom_fb_prusing difference ΔVdc and the control gain (proportional gain PG andintegration gain IG) determined according to difference ΔVdc, andcorrects the calculated feedback preliminary voltage control valueVdccom_fb_pr using the conversion ratio Vstd/Vm to calculate feedbackvoltage control value Vdccom_fb.

In the second embodiment, feedback voltage control value calculationunit 52A corrects difference ΔVdc using conversion ratio Vstd/Vm.Specifically, when output voltage Vm is equal to reference voltage Vstd,corrector 524A multiplies difference ΔVdc from subtractor 521 by theconversion ratio Vstd/Vm=1 to output a correction difference ΔVdccconstituted of difference ΔVdc. When output voltage Vm is greater thanreference voltage Vstd, corrector 524A multiplies difference ΔVdc byconversion ratio Vstd/Vm<1 to output a correction difference ΔVdccconstituted of ΔVdc×(Vstd/Vm). When output voltage Vm is lower thanreference voltage Vstd, corrector 524A multiplies difference ΔVdc byconversion ratio VstdVm>1 to output correction difference ΔVdccconstituted of ΔVdc×(Vstd/Vm).

When output voltage Vm is equal to reference voltage Vstd, feedbackvoltage control value Vdccom_fbv2=Vdccom_fb0 is established, whereby thefollow-up property of output voltage Vm to voltage control value Vdccomcorresponds to pattern 1 of FIG. 8. When output voltage Vm is higherthan reference voltage Vstd, feedback voltage control valueVdccom_fbv2=Vdccom_fb1 is established, whereby the follow-up property ofoutput voltage Vm with respect to voltage control value Vdccomcorresponds to pattern 2 shown in FIG. 8. In other words, by correctingdifference ΔVdc with conversion ratio Vstd<1, the follow-up property(represented by curve k3) deviating from the reference property(represented by curve k2) matches the reference property. When outputvoltage Vm is lower than reference voltage Vstd, feedback voltagecontrol value Vdccom_fbv2=Vdccom_fb2 is established, whereby thefollow-up property of output voltage Vm with respect to voltage controlvalue Vdccom corresponds to pattern 3 of FIG. 8. In other words, bycorrecting difference ΔVdc with conversion ratio Vstd>1, the follow-upproperty (represented by curve k4) deviating from the reference property(represented by curve k2) matches the reference property.

Thus, when output voltage Vm deviates from reference voltage Vstd,corrector 524A corrects difference ΔVdc in accordance with outputvoltage Vm such that the follow-up property of output voltage Vm withrespect to voltage control value Vdccom is equal to the referenceproperty.

Correction difference ΔVdcc is used to set the follow-up property ofoutput voltage Vm with respect to voltage control value Vdccom equal tothe reference property.

Feedback voltage control value calculation units 52 and 52A are commonin the feature of calculating feedback voltage control values Vdccom_fband Vdccom_fbv2 where the follow-up property of output voltage Vm tovoltage control value Vdccom is equal to the reference property.

The second embodiment is characterized in that difference ΔVdc betweenoutput voltage Vm and voltage control value Vdccom is corrected inaccordance with output voltage Vm, and feedback voltage control valueVdccom_fbv2 (=Vdccom_fb) where the follow-up property of output voltageVm to voltage control value Vdccom is equal to the reference voltage iscalculated using the corrected correction difference ΔVdcc. Theproportional gain PG and integration gain IG constituting the controlgain are not corrected.

An operation of controlling voltage conversion in the second embodimentwill be described with reference to FIG. 14. The flow chart of FIG. 14differs from the flow chart of FIG. 9 only in that steps S4 and S5 inthe flow chart of FIG. 9 are replaced with steps S4 a and S5 a,respectively.

Following step S3, corrector 524A receives difference ΔVdc fromsubtracter 521 and output voltage Vm from voltage sensor 13 to correctdifference ΔVdc based on equation (6) (step 4 a). Corrector 524Aprovides correction difference ΔVdcc to PI controller 523A.

PI controller 523A receives the control gain from gain determinationunit 522 (proportional gain PG and integration gain IG), and correctiondifference ΔVdcc from corrector 524A to calculate feedback voltagecontrol value Vdccom_fbv2 (=Vdccom_fb) by equation (7), and provides thecalculated feedback voltage control value Vdccom_fbv2 to duty ratiocalculation unit 541 (step S5 a).

Then, steps S6-S8 set forth before are executed, and the series ofoperations ends (step S9).

In the present invention, voltage-up converter 12 and also feedbackvoltage control value calculation unit 52A and duty ratio converter 54of control device 30A constitute the “voltage conversion apparatus”.

In the present invention, feedback voltage control value calculationunit 52A and duty ratio converter 54 constitute the “control means”controlling voltage-up converter 12 identified as the voltage converter.

PI controller 523A constitutes the “computing element” calculatingfeedback voltage control value Vdccom_fb.

Feedback voltage control value calculation unit 52A calculates feedbackvoltage control value Vdccom_fbv2 (=Vdccom_fb) where the follow-upproperty of output voltage Vm to voltage control value Vdccom is equalto the reference voltage, likewise feedback voltage control valuecalculation unit 52. Therefore, the feedback voltage control valuecalculation unit in the present invention is arbitrary as long as thefeedback voltage control value where the follow-up property of outputvoltage Vm to voltage control value Vdccom is equal to the referenceproperty is calculated by correcting difference ΔVdc or feedbackpreliminary voltage control value Vdccom_fb_pr by conversion ratioVstd/Vm.

The voltage conversion method of the present invention is a voltageconversion method of converting the direct current voltage into outputvoltage Vm under feedback control in accordance with the flow chart ofFIG. 14.

Furthermore, feedback control in feedback voltage control valuecalculation unit 52A and duty ratio converter 54 is carried out inpractice by a CPU (Central Processing Unit). The CPU reads out a programincluding respective steps of the flow chart of FIG. 14 from a ROM (ReadOnly Memory), and executes the program read out to control voltageconversion of the direct current voltage into output voltage Vm inaccordance with the flow chart of FIG. 14. Therefore, the ROM isequivalent to a computer (CPU) readable recording medium on which aprogram including respective steps in the flow chart of FIG. 14 isrecorded.

The voltage conversion method of the present invention may have steps S4and S5 of FIG. 9 or steps S4 a and S5 a of FIG. 14 replaced with thestep of “calculating feedback voltage control value Vdccom_fb where thefollow-up property of output voltage Vm with respect to voltage controlvalue Vdccom is equal to the reference property, based on differenceΔVdc and the control gain (proportional gain PG and integration gainIG)”.

This step is also applicable to a program recorded in a ROM.

The remaining elements are similar to those of the first embodiment.

In accordance with the second embodiment, the voltage conversionapparatus includes control means correcting the difference between theoutput voltage and the designated voltage into the difference where thefollow-up property of the output voltage with respect to the voltagecontrol value is equal to the reference property, and calculating thefeedback voltage control value using the corrected correction differencein the feedback control where the output voltage corresponding to aconverted version of the direct current voltage from the DC power supplyis equal to the voltage control value. Therefore, the direct currentvoltage can be converted into the output voltage while keeping thefollow-up property of the output voltage with respect to the voltagecontrol value constant.

Third Embodiment

Referring to FIG. 15, a motor driver 100B including a voltage conversionapparatus according to a third embodiment of the present inventiondiffers from motor driver 100 only in that a control device 30B isprovided instead of control device 30 of motor driver 100.

Referring to FIG. 16, control device 30B differs from control device 30only in that a motor torque control means 301B is provided instead ofmotor torque control means 301 of control device 30.

Motor torque control means 301B generates a signal PWMI by a methodidentical to that of motor torque control means 301, and also generatessignal PWU in accordance with the method that will be describedafterwards to provide the generated signal PWU to voltage-up converter12.

Referring to FIG. 17, motor torque control means 301B differs from motortorque control means 301 only in that a feedback voltage control valuecalculation unit 52B is provided instead of feedback voltage controlvalue calculation unit 52 of motor torque control means 301, and a dutyratio converter 54A is provided instead of duty ratio converter 54.

Feedback voltage control value calculation unit 52B calculates feedbackvoltage control value Vdccom_fbv3 based on voltage control value Vdccomfrom inverter input voltage control value calculation unit 50 and outputvoltage Vm from voltage sensor 13 to provide the calculated feedbackvoltage control value Vdccom_fbv3 to duty ratio converter 54A. Feedbackvoltage control value calculation unit 52B functions likewise feedbackvoltage control value calculation unit 52.

Duty ratio converter 54A generates and provides to voltage-up converter12 a signal PWU required such that the follow-up property of outputvoltage Vm with respect to voltage control value Vdccom is equal to thereference property, based on feedback voltage control value Vdccom_fbv3,and compensation ratios Rcom, 1−Rcom from feedback voltage control valuecalculation unit 52B, and output voltage Vm from voltage sensor 13.

Referring to FIG. 18, feedback voltage control value calculation unit52B differs from feedback voltage control value calculation unit 52 onlyin that corrector 524 of a feedback voltage control value calculationunit 52 is removed.

Therefore, feedback voltage control value calculation unit 52B insertsdifference ΔVdc between output voltage Vm and voltage control valueVdccom, and the control gain (proportional gain PG and integration gainIG) into equation (1) to calculate feedback voltage control valueVdccom_fbv3. Feedback voltage control value calculation unit 52Bprovides the calculated feedback voltage control value Vdccom_fbv3 toduty ratio calculation unit 541.

Namely, feedback voltage control value calculation unit 52B calculatesand provides to duty ratio calculation unit 541 a feedback voltagecontrol value Vdccom_fbv3 determined from difference ΔVdc withoutconducting the correction as in the first and second embodiments.

Feedback voltage control value Vdccom_fbv3 is equal to feedbackpreliminary voltage control value Vdccom_fb_pr in the first embodiment.

Duty ratio converter 54A is similar to duty ratio converter 54, providedthat a corrector 544 is added to duty ratio converter 54. Corrector 544is disposed between duty ratio calculation unit 541 and adder 542.Corrector 544 receives duty ratio DRO from duty ratio calculation unit541 and output voltage Vm from voltage sensor 13 to correct duty ratioDRO through the following equation using output voltage Vm to calculatecorrection duty ratio DRC. $\begin{matrix}{{DRC} = {{DR0} \times \frac{Vstd}{Vm}}} & (10)\end{matrix}$

Then, corrector 544 provides correction duty ratio DRC to adder 542.

Corrector 544 divides reference voltage Vstd by output voltage Vm tocalculate a conversion ratio that is required to convert output voltageVm into reference voltage Vstd where the follow-up property of outputvoltage Vm with respect to voltage control value Vdccom is equal to thereference property. Corrector 544 multiplies the calculated conversionratio by duty ratio DRO to calculate a correction duty ratio DRC wherethe follow-up property of output voltage Vm with respect to voltagecontrol value Vdccom is equal to the reference property.

As set forth above, feedback voltage control value calculation unit 52Bcalculates feedback voltage control value Vdccom_fbv3 based ondifference ΔVdc alone, without any correction. Duty ratio calculationunit 541 calculates duty ratio DRO based on feedback voltage controlvalue Vdccom_fbv3.

In this case, duty ratio DRO is constant even if output voltage Vmvaries as long as difference ΔVdc is constant since the duty ratio iscalculated based on difference ΔVdc alone. Specifically, duty ratiocalculation unit 541 calculates the duty ratio based on feedback voltagecontrol value Vdccom_fbv3 to output to corrector 544 a duty ratio DROidentical to duty ratio DR0 shown in FIG. 6.

Corrector 544 corrects the duty ratio DRO from duty ratio calculationunit 541 based on equation (10) to output correction duty ratio DRC toadder 542.

When output voltage Vm matches reference voltage Vstd, corrector 544multiplies duty ratio DRO from duty ratio calculation unit 541 by theconversion ratio Vstd/Vm=1 to provide correction duty ratio DRCconstituted of duty ratio DRO (=DR0: refer to FIG. 6) to adder 542. Whenoutput voltage Vm is higher than reference voltage Vstd, corrector 544multiplies duty ratio DRO from duty ratio calculation unit 541 byconversion ratio Vstd/Vm<1 to output to adder 542 a correction dutyratio DRC constituted of duty ratio DR1 shown in FIG. 6. When outputvoltage Vm is lower than reference voltage Vstd, corrector 544multiplies duty ratio DRO from duty ratio calculation unit 541 byconversion ratio Vstd/Vm>1 to output to adder 542 a correction dutyratio DRC constituted of duty ratio DR2 shown in FIG. 6.

Then, adder 542 adds compensation ratios Rcom, 1−Rcom from forwardcompensator 525 to correction duty ratio DRC from corrector 544 toprovide the compensation duty ratios to PWM signal converter 543.

Specifically, when output voltage Vm is equal to reference voltage Vstd,adder 542 adds compensation ratios Rcom, 1−Rcom to correction duty ratioDRC constituted of duty ratio DR0 shown in FIG. 6 to provide thecompensation duty ratio constituted of duty ratios DR0U, DR0L shown inFIG. 6 to PWM signal converter 543. When output voltage Vm is higherthan reference voltage Vstd, adder 542 adds compensation ratios Rcom,1−Rcom to correction duty ratio DRC constituted of duty ratio DR1 shownin FIG. 6 to provide the compensation duty ratio constituted of dutyratios DR1U and DR1L shown in FIG. 6 to PWM signal converter 543. Whenoutput voltage Vm is lower than reference voltage Vstd, adder 542 addscompensation ratios Rcom, 1−Rcom to correction duty ratio DRCconstituted of duty ratio DR2 shown in FIG. 6 to provide compensationduty ratio constituted of duty ratios DR2U and DR2L shown in FIG. 6 toPWM signal converter 543.

PWM signal converter 543 generates and provides to voltage-up converter12 a signal PWU based on the compensation duty ratio from adder 542.Specifically, when output voltage Vm is equal to reference voltage Vstd,PWM signal converter 543 generates signals PWU0U and PWU0L shown in FIG.7 based on the compensation duty ratio constituted of duty ratios DR0Uand DR0L shown in FIG. 6, respectively, to provide a signal PWU0constituted of signals PWU0U and PWU0L to voltage-up converter 12. Whenoutput voltage Vm is higher than reference voltage Vstd, PWM signalconverter 543 generates signals PWU1U and PWU1L shown in FIG. 7 based onthe compensated duty ratio of duty ratios DR1U and DR1L shown in FIG. 6,respectively, to provide a signal PWU1 constituted of signals PWU1U andPWU1L to voltage-up converter 12. When output voltage Vm is lower thanreference voltage Vstd, PWM signal converter 543 generates signals PWU2Uand PWU2L shown in FIG. 7 based on the compensation duty ratioconstituted of duty ratios DR2U and DR2L shown in FIG. 6, respectively,to provide a signal PWU2 constituted of signals PWU2U and PWU2L tovoltage-up converter 12.

Since duty ratio DRO output from duty ratio calculation unit 541 is nota duty ratio calculated taking into account variation in output voltageVm, duty ratio DRO is compensated in accordance with output voltage Vmin the third embodiment to calculate correction duty ratio DRC where thefollow-up property of output voltage Vm with respect to voltage controlvalue Vdccom is equal to the reference property.

As a result, the direct current voltage Vb from DC power supply B isconverted into output voltage Vm with the follow-up property of outputvoltage Vm to voltage control value Vdccom maintained at the referenceproperty.

An operation of controlling voltage conversion in the third embodimentwill be described with reference to FIG. 19. The flow chart of FIG. 19differs from the flow chart of FIG. 9 only in that steps S5-S7 of theflow chart of FIG. 9 are replaced with steps S51-S53, respectively.

Following step S4, duty ratio calculation unit 541 calculates duty ratioDRO based on feedback voltage control value Vdccom_fbv3 to provide thecalculated duty ratio DRO to corrector 544 (step S51). Corrector 544corrects duty ratio DRO based on equation (10), and provides correctedduty ratio DRC to adder 542 (step S52).

Adder 542 adds compensation ratios Rcom, 1−Rcom from forward compensator525 to correction duty ratio DRC from corrector 544 to provide acompensation duty ratio to PWM signal converter 543. PWM signalconverter 543 generates a signal PWU0 (or PWU1 or PWU2) based on thecompensation duty ratio from adder 542 (step S53). Then, step S8 isexecuted, and the series of operations ends (step S9).

In the present invention, voltage-up converter 12 and also feedbackvoltage control value calculation unit 52B and duty ratio converter 54Aof control device 30B constitute the “voltage conversion apparatus”.

In the present embodiment, feedback voltage control value calculationunit 52B and duty ratio converter 54A constitute the “control means” tocontrol voltage-up converter 12 identified as the voltage converter.

Duty ratio calculation unit 541 of the third embodiment constitutes the“computing element” for calculating a preliminary duty ratio.

The voltage conversion method of the present invention conducts feedbackcontrol in accordance with the flow chart of FIG. 19 to convert thedirect current voltage into output voltage Vm.

The feedback control in feedback voltage control value calculation unit52B and duty ratio conversion unit 54A is in practice carried out by theCPU (Central Processing Unit). The CPU reads out a program includingrespective steps of the flow chart of FIG. 19 from a ROM (Read OnlyMemory) to execute the program read out to control voltage conversion ofthe direct current voltage into output voltage Vm in accordance with theflow chart of FIG. 19. Therefore, the ROM is equivalent to a computer(CPU)—readable recording medium with a program including respectivesteps of the flow chart of FIG. 19 recorded thereon.

The remaining elements are similar to those of the first embodiment.

In accordance with the third embodiment, the voltage conversionapparatus includes control means correcting the duty ratio calculatedbased on the difference between the output voltage and the designatedvoltage into the duty ratio where the follow-up property of the outputvoltage with respect to the voltage control value is equal to thereference property, and controlling the voltage-up converter using thecorrected duty ratio in the feedback control such that the outputvoltage corresponding to a converted version of the direct currentvoltage from the DC power supply is equal to the voltage control value.Therefore, the direct current voltage can be converted into the outputvoltage while keeping the follow-up property of the output voltage withrespect to the voltage control value constant.

Fourth Embodiment

Referring to FIG. 20, a motor driver 100C incorporating a voltageconversion apparatus according to a fourth embodiment differs from motordriver 100 only in that a current sensor 28 and an inverter 31 are addedto motor driver 100, and control device 30 of motor driver 100 isreplaced with a control device 30C.

Capacitor C2 receives output voltage Vm from voltage-up converter 12 vianodes N1 and N2 to smooth the received output voltage Vm, and suppliesthe smoothed output voltage Vm to inverter 14 as well as to inverter 31.Current sensor 24 detects and provides to control device 30C a motorcurrent MCRT1. Inverter 14 converts the direct current voltage fromcapacitor C2 into an alternating voltage based on a signal PWMI1 fromcontrol device 30C to drive alternating current motor M1, and convertsthe alternating voltage generated by alternating current motor M1 into adirect current voltage based on a signal PWMC1.

Inverter 31 has a configuration similar to that of inverter 14. Inverter31 converts the direct current voltage from capacitor C2 into analternating voltage based on a signal PWMI2 from control device 30C todrive alternating current motor M2, and converts the alternating voltagegenerated by alternating current motor M2 into a direct current voltagebased on a signal PWMC2. Current sensor 28 detects and provides tocontrol device 30C a motor current MCRT2 flowing to each phase ofalternating current motor M2.

Control device 30C receives direct current voltage Vb output from DCpower supply B from voltage sensor 10, receives motor currents MCRT1 andMCRT2 from current sensors 24 and 28, respectively, receives outputvoltage Vm of voltage-up converter 12 (the input voltage to inverters 14and 31) from voltage sensor 13 and receives torque control values TR1and TR2 and motor rotation numbers MRN1 and MRN2 from the external ECU.Control device 30C generates and provides to inverter 14 signal PWMI1required for switching control of NPN transistors Q3-Q8 of inverter 14when inverter 14 drives alternating current motor M1 by the method setforth above, based on voltage Vb, output voltage Vm, motor currentMCRT1, torque control value TR1 and motor rotation number MRN1.

Furthermore, control device 30C generates and provides to inverter 31 asignal PWMI2 required for switching control of NPN transistors Q3-Q8 ofinverter 31 when inverter 31 drives alternating current motor M2 by themethod set forth above, based on direct current voltage Vb, outputvoltage Vm, motor current MCRT2, torque control value TR2 and motorrotation number MRN2.

When inverter 14 or 31 drives alternating current motor M1 or M2,control device 30C generates and provides to voltage-up converter 12 asignal PWU required for switching control of NPN transistors Q1 and Q2of voltage-up converter 12 by the method set forth above (any of themethods of the first to third embodiments), based on direct currentvoltage Vb, output voltage Vm, motor current MCRT1 (or MCRT2), torquecontrol value TR1 (or TR2), and motor rotation number MRN1 (or MRN2).

Furthermore, control device 30C generates a signal PWMC1 required toconvert the alternating voltage generated by alternating current motorM1 in the regenerative braking mode into the direct current voltage or asignal PWMC2 required to convert the alternating voltage generated byalternating current motor M2 in the regenerative braking mode into thedirect current voltage to output the generated signal PWMC1 or PWMC2 toinverter 14 or inverter 31, respectively. In this case, control device30C generates and provides to voltage-up converter 12 a signal PWD tocontrol voltage-up converter 12 such that the direct current voltagefrom inverter 14 or 31 is down-converted to charge DC power supply B.

Control device 30C generates and provides to system relays SR1 and SR2signal SE to turn on system relays SR1 and SR2.

Referring to FIG. 21, control device 30C includes a motor torque controlmeans 301C and voltage conversion control means 302A. Motor torquecontrol means 301C generates and provides to inverters 14 and 31 signalsPWMI1 and PWMI2, respectively, based on motor currents MCRT1 and 2,torque control values TR1 and 2, motor rotation numbers MRN1 and 2,direct current voltage Vb and output voltage Vm. Motor torque controlmeans 301C generates and provides to voltage-up converter 12 a signalPWU based on direct current voltage Vb, output voltage Vm, motor currentMCRT1 (or MCRT2), torque control value TR1 (or TR2), and motor rotationnumber MRN1 (or MRN2).

Upon receiving from the external ECU a signal RGE indicating that thehybrid vehicle or electric vehicle in which motor driver 100 isincorporated has entered the regenerative braking mode, voltageconversion control means 302A generates signals PWMC1 and PWMC2 andsignal PWD to provide generated signals PWMC1 and PWMC2 to inverters 14and 31, respectively, and signal PWD to voltage-up converter 12.

Referring to FIG. 22, motor torque control means 301C has aconfiguration identical to that of motor torque control means 301 (referto FIG. 3). It is to be noted that motor torque control means 301Cdiffers from motor torque control means 301 in that motor torque controlmeans 301 generates signals PWMI1, 2 and signal PWU based on two torquecontrol values TRI, 2, two motor currents MCT1, 2, and two motorrotation numbers MRN1, 2 to control inverters 14, 31, and voltage-upconverter 12 based on the generated signals PWMI1, PWMI2, and PWU,respectively.

Motor control phase voltage calculation unit 40 calculates the voltageto be applied to each phase of alternating current motor M1 based onoutput voltage Vm from voltage-up converter 12, motor current MCRT1, andtorque control value TR1, and calculates the voltage to be applied toeach phase of alternating current motor M2 based on output voltage Vm,motor current MCRT2, and torque control value TR2. Motor control phasevoltage calculation unit 40 provides the calculated voltage foralternating current motor M1 or M2 to PWM signal converter 42 for theinverter.

Upon receiving the voltage for alternating current motor M1 from motorcontrol phase voltage calculation unit 40, inverter PWM signal converter42 generates and provides to inverter 14 signal PWMI1 based on thereceived voltage. Upon receiving the voltage for alternating currentmotor M2 from motor control phase voltage calculation unit 40, inverterPWM signal converter 42 generates and provides to inverter 31 signalPWMI2 based on the received voltage.

Inverter input voltage control value calculation unit 50 calculates avoltage control value Vdccom based on torque control value TR1 and motorrotation number MRN1 (or torque control value TR1 and motor rotationnumber MRN2), and outputs the calculated voltage control value Vdccom tofeedback voltage control value calculation unit 52.

As described in the first embodiment, based on voltage control valueVdccom, output voltage Vm and battery voltage Vb, feedback voltagecontrol value calculation unit 52 calculates feedback voltage controlvalue Vdccom_fb and compensation ratios Rcom, 1−Rcom where the follow-upproperty of output voltage Vm with respect to voltage control valueVdccom is equal to the reference property to provide the calculatedfeedback voltage control value Vdccom_fb and compensation ratios Rcom,1−Rcom to duty ratio converter 54.

Duty ratio converter 54 generates and provides to voltage-up converter12 a signal PWU (any of signals PWU0, PWU1, and PWU2) as described inthe first embodiment.

Accordingly, the follow-up property of output voltage Vm with respect tovoltage control value Vdccom is maintained at the reference property,even in the case where two alternating current motors M1 and M2 areconnected, and direct current voltage Vb output from DC power supply Bis converted into output voltage Vm.

In motor torque control means 301C, a feedback voltage control valuecalculation unit 52A may be applied instead of feedback voltage controlvalue calculation unit 52.

Furthermore, in motor torque control means 301C, feedback voltagecontrol value calculation unit 52B and duty ratio converter 54A may beapplied instead of feedback voltage control value calculation unit 52and duty ratio converter 54, respectively.

When feedback voltage control value calculation unit 52 and duty ratioconverter 54 are applied to motor torque control means 301C, voltageconversion of direct current voltage Vb into output voltage Vm thatmaintains the follow-up property of output voltage Vm with respect tovoltage control value Vdccom at the reference property is under controlin accordance with the flow chart of FIG. 9.

When feedback voltage control value calculation unit 52A and duty ratioconverter 54 are applied to motor torque control means 301C, voltageconversion of direct current voltage Vb into output voltage Vm thatmaintains the follow-up property of output voltage Vm with respect tovoltage control value Vdccom at the reference property is under controlin accordance with the flow chart of FIG. 14.

When feedback voltage control value calculation unit 52B and duty ratioconverter 54A are applied to motor torque control means 301C, voltageconversion of direct current voltage Vb into output voltage Vm thatmaintains the follow-up property of output voltage Vm with respect tovoltage control value Vdccom at the reference property is under controlin accordance with the flow chart of FIG. 19.

In motor driver 100C, the number of motors to be driven is not limitedtwo; three or more motors can be driven. For example, alternatingcurrent motor M1, alternating current motor M2, and the engine can beconnected to a planetary gear mechanism (engine output shaft isconnected to a carrier, alternating current motor M1 is connected to asun gear, and alternating current motor M2 is connected to a ring gear),and the output shaft of the ring gear is configured such that the frontwheel driving shaft, for example, of the vehicle is rotated, and thethird alternating current motor can be arranged in the vehicle such thatthe rear wheel driving shaft is rotated. The present invention can bearranged appropriately in accordance with the various configurations ofthe electric vehicle and hybrid vehicle.

An entire operation of motor driver 100C will be described hereinafterwith reference to FIG. 20 again. Description is provided based oncontrol device 30C including feedback voltage control value calculationunit 52 and duty ratio calculation unit 54.

Upon initiation of the entire operation, control device 30C generatesand provides to system relays SR1 and SR2 signal SE, whereby systemrelays SR1 and SR2 are turned on. DC power supply B provides the directcurrent voltage to voltage-up converter 12 via system relays SR1 andSR2.

Voltage sensor 10 detects direct current voltage Vb output from DC powersupply B to provide the detected direct current voltage Vb to controldevice 30C. Voltage sensor 13 detects voltage Vm across capacitor C2 toprovide the detected voltage Vm to control device 30C. Current sensor 24detects and provides to control device 30C motor current MCRT1 flowingto alternating current motor M1. Current sensor 28 detects and providesto control device 30C motor current MCRT2 flowing to alternating currentmotor M2. Control device 30C receives torque control values TR1, 2 andmotor rotation numbers MRN1, 2 from the external ECU.

In response, control device 30C generates and provides to inverter 14signal PWMI1 by the method set forth above, based on direct currentvoltage Vb, output voltage Vm, motor current MCRT1, torque control valueTR1 and motor rotation number MRN1. Control device 30C generates andprovides to inverter 31 signal PWMI2 by the method set forth above basedon direct current voltage Vb, output voltage Vm, motor current MCRT2,torque control value TR2 and motor rotation number MRN2.

Further, when inverter 14 (or 31) drives alternating current motor M1(or M2), control device 30C generates and provides to voltage-upconverter 12 signal PWU required for switching control of NPNtransistors Q1 and Q2 of voltage-up converter 12 by the method set forthabove (first embodiment), based on direct current voltage Vb, outputvoltage Vm, motor current MCRT1 (or MCRT2), torque control value TR1 (orTR2), and motor rotation number MRN1 (or MRN2).

Specifically, control device 30C calculates feedback voltage controlvalue Vdccom_fb where the follow-up property of output voltage Vm withrespect to voltage control value Vdccom is equal to the referenceproperty, as well as compensation ratios Rcom, 1−Rcom, based on voltagecontrol value Vdccom, output voltage Vm and battery voltage Vb togenerate and provide to voltage-up converter 12 signal PWU (any ofsignals PWU0, PWU1 and PWU2) based on the calculated feedback voltagecontrol value Vdccom_fb and compensation ratios Rcom, 1−Rcom.

Accordingly, voltage-up converter 12 boosts the direct current voltagefrom DC power supply B while maintaining the follow-up property ofoutput voltage Vm with respect to voltage control value Vdccom at thereference property in accordance with signal PWU (any of signals PWU0,PWU1 and PWU2), and supplies the boosted direct current voltage tocapacitor C2 via nodes N1 and N2. Inverter 14 converts the directcurrent voltage smoothed by capacitor C2 into the alternating voltage bysignal PWMI1 from control device 30C to drive alternating current motorM1. Further, inverter 31 converts the direct current voltage smoothed bycapacitor C2 into the alternating voltage by signal PWMI2 from controldevice 30C to drive alternating current motor M2. Accordingly,alternating current motor M1 generates the torque designated by torquecontrol value TR1, whereas alternating current motor M2 generates thetorque designated by torque control value TR2.

When the hybrid vehicle or electric vehicle in which motor driver 100Cis incorporated is in the regenerative braking mode, control device 30Creceives signal RGE from the external ECU to generate and provide toinverters 14 and 31 signals PWMC1, 2, respectively, in accordance withthe received signal RGE, and to generate and provide to voltage-upconverter 12 signal PWD.

Accordingly, inverter 14 converts the alternating voltage generated atalternating current motor M1 into the direct current voltage inaccordance with signal PWMC1 to supply the converted direct currentvoltage to voltage-up converter 12 via capacitor C2. Further, inverter31 converts the alternating voltage generated by alternating currentmotor M2 into the direct current voltage in accordance with signal PWMC2to supply the converted direct current voltage to voltage-up converter12 via capacitor C2. Voltage-up converter 12 receives the direct currentfrom capacitor C2 via nodes N1 and N2 to down-convert the receiveddirect current voltage by signal PWD, and supplies the down-converteddirect current voltage to DC power supply B. Accordingly, DC powersupply B is charged by the power generated by alternating current motorM1 or M2.

In the case where control device 30C includes feedback voltage controlvalue calculation unit 52A and duty ratio calculation unit 54, theentire operation of motor driver 100C is similar to the above-describedoperation, provided that the boosting operation by voltage-up converter12 is carried out in accordance with the flow chart of FIG. 14.

Further, in the case where control device C includes feedback voltagecontrol value calculation unit 52B and duty ratio calculation unit 54A,the entire operation of motor driver 100C is similar to theabove-described operation, provided that the boosting operation ofvoltage-up converter 12 is carried out in accordance with the flow chartof FIG. 19.

The remaining elements are similar to those of the first to thirdembodiments.

In accordance with the fourth embodiment, the voltage conversionapparatus includes control means for controlling the voltage-upconverter such that the follow-up property of the output voltage to thevoltage control value is equal to the reference property, under feedbackcontrol such that the output voltage that is a converted version of thedirect current voltage from the DC power supply is equal to the voltagecontrol value. Since the output voltage converted by the voltageconversion apparatus is provided to a plurality of invertors that drivea plurality of motors, the direct current voltage can be converted intothe output voltage while keeping the follow-up property of the outputvoltage with respect to the voltage control value constant even in thecase where a plurality of motors are connected.

Although the above description is based on a case where the presentinvention is applied to feedback control using proportional gain PG andintegration gain IG, the present invention may be applied to feedbackcontrol using proportional gain PG, integration gain IG, and aderivative gain DG.

It will be understood that the embodiments disclosed herein are by wayof illustration and example only, and is not to be taken by way oflimitation. The scope of the present invention is defined by theappended claims rather than by the description of the embodiments setforth above. All changes that fall within the limits and bounds of theclaims, or equivalence thereof are therefore intended to be embraced bythe claims.

INDUSTRIAL APPLICABILITY

The present invention is applied to a voltage conversion apparatusconverting the direct current voltage into the output voltage such thatthe follow-up property of the output voltage with respect to thedesignated voltage is constant.

1. A voltage conversion apparatus converting a direct current voltagefrom a DC power supply into an output voltage such that said outputvoltage is equal to a designated voltage, comprising: a voltageconverter altering a voltage level of said direct current voltage toprovide an output voltage, detection unit detecting the output voltageoutput from said voltage converter, and control unit controlling saidvoltage converter such that a follow-up property of said output voltagewith respect to said designated voltage in feedback control isconsistent with a reference property, and said output voltage is equalto said designated voltage, based on said detected output voltage andsaid designated voltage.
 2. The voltage conversion apparatus accordingto claim 1, wherein said voltage converter includes a chopper circuit,said control unit comprises a feedback voltage control value calculationunit detecting a difference between said output voltage and saiddesignated voltage to determine a control gain in said feedback controlin accordance with the detected difference, and calculating a feedbackvoltage control value in said feedback control such that said follow-upproperty is equal to said reference property based on the determinedcontrol gain, said output voltage, and said difference, a duty ratiocalculation unit calculating a switching duty ratio of said choppercircuit, based on said calculated feedback voltage control value, and aswitching signal generation unit generating a switching signal havingsaid switching duty ratio, and providing the generated switching signalto said chopper circuit.
 3. The voltage conversion apparatus accordingto claim 2, wherein said feedback voltage control value calculation unitcalculates said feedback voltage control value by correcting a feedbackpreliminary voltage control value calculated using said control gainsuch that said follow-up property is equal to said reference property.4. The voltage conversion apparatus according to claim 3, wherein saidfeedback voltage control value calculation unit comprises a subtractercalculating a difference between said output voltage and said designatedvoltage, a gain determination unit determining said control gain basedon said difference, a computing element calculating said feedbackpreliminary voltage control value based on said determined control gain,and a corrector correcting said feedback preliminary voltage controlvalue by converting said output voltage into a reference voltage wheresaid follow-up property is equal to said reference property to outputsaid feedback voltage control value.
 5. The voltage conversion apparatusaccording to claim 4, wherein said corrector calculates a ratio of saidreference voltage to said output voltage, and multiplies the calculatedresult by said feedback preliminary voltage control value to correctsaid feedback preliminary voltage control value.
 6. The voltageconversion apparatus according to claim 2, wherein said feedback voltagecontrol value calculation unit calculates said feedback voltage controlvalue by correcting said difference such that said follow-up property isequal to said reference property.
 7. The voltage conversion apparatusaccording to claim 6, wherein said feedback voltage control valuecalculation unit comprises a subtracter calculating a difference betweensaid output voltage and said designated voltage, a corrector correctingsaid difference such that said follow-up property is equal to saidreference property, a gain determination unit determining said controlgain based on said difference, and a computing element calculating saidfeedback voltage control value based on said determined control gain andsaid corrected difference.
 8. The voltage conversion apparatus accordingto claim 7, wherein said corrector corrects said difference byconverting said output voltage into a reference voltage where saidfollow-up property is equal to said reference property.
 9. The voltageconversion apparatus according to claim 8, wherein said correctorcalculates a ratio of said reference voltage to said output voltage, andcorrects said difference by multiplying the calculated result by saiddifference.
 10. The voltage conversion apparatus according to claim 1,wherein said voltage converter includes of a chopper circuit, saidcontrol unit comprises a feedback voltage control value calculation unitdetecting a difference between said output voltage and said designatedvoltage to determine a control gain in said feedback control inaccordance with the detected difference, and calculating a feedbackpreliminary voltage control value in said feedback control based on thedetermined control gain, said output voltage, and said difference, aduty ratio calculation unit calculating a switching duty ratio of saidchopper circuit such that said follow-up property is equal to saidreference property, based on said calculated feedback preliminaryvoltage control value and said output voltage, and a switching signalgeneration unit generating a switching signal having said switching dutyratio, and providing the generated switching signal to said choppercircuit.
 11. The voltage conversion apparatus according to claim 10,wherein said duty ratio calculation unit calculates said switching dutyratio by correcting a preliminary duty ratio calculated using saidfeedback preliminary voltage control value such that said follow-upproperty is equal to said reference property.
 12. The voltage conversionapparatus according to claim 11, wherein said duty ratio calculationunit comprises a computing element calculating said preliminary dutyratio in accordance with said feedback preliminary voltage controlvalue, and a corrector correcting said preliminary duty ratio such thatsaid follow-up property is equal to said reference property.
 13. Thevoltage conversion apparatus according to claim 12, wherein saidcorrector corrects said preliminary duty ratio by converting said outputvoltage into a reference voltage where said follow-up property is equalto said reference property.
 14. The voltage conversion apparatusaccording to claim 13, wherein said corrector calculates a ratio of saidreference voltage to said output voltage, and corrects said preliminaryduty ratio by multiplying the calculated result by said preliminary dutyratio.
 15. A voltage conversion method of converting a direct currentvoltage from a DC power supply into an output voltage under feedbackcontrol such that said output voltage is equal to a designated voltage,said method comprising: a first step of detecting said output voltage, asecond step of detecting a difference between said designated voltageand said output voltage, a third step of determining a control gain inaccordance with said detected difference, and a fourth step ofconverting said direct current voltage into said output voltage suchthat a follow-up property of said output voltage with respect to saiddesignated voltage in said feedback control is consistent with areference property, and said output voltage is equal to said designatedvoltage, based on said determined control gain, said detecteddifference, and said detected output voltage.
 16. The voltage conversionmethod according to claim 15, wherein said direct current voltage beingconverted into said output voltage by a chopper circuit, said fourthstep comprises a first substep of calculating a feedback voltage controlvalue that causes said follow-up property to match said referenceproperty in said feedback control, based on said control gain, saiddifference, and said output voltage, a second substep of calculating aswitching duty ratio of said chopper circuit using said feedback voltagecontrol value, and a third substep of controlling said chopper circuitsuch that said output voltage is equal to said designated voltage, basedon said switching duty ratio.
 17. The voltage conversion methodaccording to claim 16, wherein said first substep includes the step ofcalculating a feedback preliminary voltage control value in saidfeedback control based on said control gain and said difference, and thestep of calculating said feedback voltage control value by correctingsaid feedback preliminary voltage control value using said outputvoltage.
 18. The voltage conversion method according to claim 17,wherein said step of calculating said feedback voltage control valueincludes the step of calculating a conversion ratio required to convertsaid output voltage into a reference voltage where said follow-upproperty is equal to said reference property, and the step ofmultiplying said feedback preliminary voltage control value by saidconversion ratio to calculate said feedback voltage control value. 19.The voltage conversion method according to claim 16, wherein said firstsubstep includes the step of calculating a correction difference wheresaid follow-up property is equal to said reference property bycorrecting said difference using said output voltage, and the step ofcalculating said feedback voltage control value based on said controlgain and said correction difference.
 20. The voltage conversion methodaccording to claim 19, wherein said step of calculating said correctiondifference includes the step of calculating a conversion ratio requiredto convert said output voltage into a reference voltage where saidfollow-up property is equal to said reference property, and the step ofmultiplying said difference by said conversion ratio to calculate saidcorrection difference.
 21. The voltage conversion method according toclaim 15, wherein said direct current voltage being converted into saidoutput voltage by a chopper circuit, said fourth step comprises a firstsubstep of calculating a feedback preliminary voltage control value insaid feedback control based on said control gain and said difference, asecond substep of calculating a preliminary switching duty ratio of saidchopper circuit based on said feedback preliminary voltage controlvalue, a third substep of correcting said preliminary switching dutyratio using said output voltage to calculate a switching duty ratiowhere said follow-up property is equal to said reference property, and afourth substep of controlling said chopper circuit such that outputvoltage is equal to said designated voltage, based on said switchingduty ratio.
 22. The voltage conversion method according to claim 21,wherein said third substep includes the step of calculating a conversionratio required to convert said output voltage into a reference voltagewhere said follow-up property is equal to said reference property, andthe step of multiplying said preliminary switching duty ratio by saidconversion ratio to calculate said switching duty ratio.
 23. Acomputer-readable recording medium with a program recorded thereon toallow a computer to execute control of voltage conversion of convertinga direct current voltage from a DC power supply into an output voltageunder feedback control such that said output voltage is equal to adesignated voltage, said computer executing: a first step of detectingsaid output voltage, a second step of detecting a difference betweensaid designated voltage and said output voltage, a third step ofdetermining a control gain in accordance with said detected difference,and a fourth step of converting said direct current voltage into saidoutput voltage such that a follow-up property of said output voltagewith respect to said designated voltage in said feedback control isconsistent with a reference property, and said output voltage is equalto said designated voltage, based on said determined control gain, saiddetected difference, and said detected output voltage.
 24. Thecomputer-readable recording medium recorded with a program thereon to beexecuted by a computer according to claim 23, wherein said directcurrent voltage being converted into said output voltage by a choppercircuit, said fourth step comprises a first substep of calculating afeedback voltage control value that causes said follow-up property tomatch said reference property in said feedback control, based on saidcontrol gain, said difference, and said output voltage, a second substepof calculating a switching duty ratio of said chopper circuit using saidfeedback voltage control value, and a third substep of controlling saidchopper circuit such that said output voltage is equal to saiddesignated voltage, based on said switching duty ratio.
 25. Thecomputer-readable recording medium recorded with a program thereon to beexecuted by a computer according to claim 24, wherein said first substepincludes the step of calculating a feedback preliminary voltage controlvalue in said feedback control based on said control gain and saiddifference, and the step of calculating said feedback voltage controlvalue by correcting said feedback preliminary voltage control valueusing said output voltage.
 26. The computer-readable recording mediumrecorded with a program thereon to be executed by a computer accordingto claim 25, wherein said step of calculating said feedback voltagecontrol value includes the step of calculating a conversion ratiorequired to convert said output voltage into a reference voltage wheresaid follow-up property is equal to said reference property, and thestep of multiplying said feedback preliminary voltage control value bysaid conversion ratio to calculate said feedback voltage control value.27. The computer-readable recording medium recorded with a programthereon to be executed by a computer according to claim 24, wherein saidfirst substep includes the step of calculating a correction differencewhere said follow-up property is equal to said reference property bycorrecting said difference using said output voltage, and the step ofcalculating said feedback voltage control value based on said controlgain and said correction difference.
 28. The computer-readable recordingmedium recorded with a program thereon to be executed by a computeraccording to claim 27, wherein said step of calculating said correctiondifference includes the step of calculating a conversion ratio requiredto convert said output voltage into a reference voltage where saidfollow-up property is equal to said reference property, and the step ofmultiplying said difference by said conversion ratio to calculate saidcorrection difference.
 29. The computer-readable recording mediumrecorded with a program thereon to be executed by a computer accordingto claim 23, wherein said direct current voltage being converted intosaid output voltage by a chopper circuit, said fourth step comprises afirst substep of calculating a feedback preliminary voltage controlvalue in said feedback control based on said control gain and saiddifference, a second substep of calculating a preliminary switching dutyratio of said chopper circuit based on said feedback preliminary voltagecontrol value, a third substep of correcting said preliminary switchingduty ratio using said output voltage to calculate a switching duty ratiowhere said follow-up property is equal to said reference property, and afourth substep of controlling said chopper circuit such that outputvoltage is equal to said designated voltage, based on said switchingduty ratio.
 30. The computer-readable recording medium recorded with aprogram thereon to be executed by a computer according to claim 29,wherein said third substep includes the step of calculating a conversionratio required to convert said output voltage into a reference voltagewhere said follow-up property is equal to said reference property, andthe step of multiplying said preliminary switching duty ratio by saidconversion ratio to calculate said switching duty ratio.